1. Field of the Invention
The present invention relates to a reflection type liquid-crystal display unit which is superior in light availability, and in which the display image is bright and easy to view.
The present application is based on Japanese Patent Application No. Hei. 10-146510, which is incorporated herein by reference.
2. Description of the Related Art
It has been attempted to develop a front light system in which a light guide plate is disposed on a liquid-crystal display element on its viewing side, through an air layer, so that incident light from the side surface of the light guide plate is emitted from one of the upper and lower surfaces through a light emitting means. Various light guide plates suitable for such a front light system have been discussed.
However, there has been a problem that a large reflection loss is produced in the air layer interposed between the light guide plate and the liquid-crystal display element, resulting in lowering of brightness or blocking of visibility by the reflected light so that the visibility is lowered on a large scale.
It is an object of the present invention to obtain a light guide plate suitable for a front light system to thereby obtain a reflection type liquid-crystal display unit which is superior in light availability, and in which the display image is bright and easy to view.
According to an aspect of the present invention, provided is a reflection type liquid-crystal display unit wherein the liquid-crystal display unit comprises: a light guide plate having an upper surface, a lower surface and a light incident surface, the light guide plate being provided with a light emitting means constituted by prismatic irregularities formed on the upper surface, so that incident light from the incidence side surface is emitted from the lower surface through the light emitting means, and the light emitted from the lower surface takes maximum intensity in a direction at an angle of 30 degrees or less with respect to a normal to a reference plane of the lower surface, while maximum intensity of leakage light from the upper surface in the direction at an angle of 30 degrees or less is not larger than ⅕ of the maximum intensity in the lower surface, while incident light from the lower surface is transmitted from the upper surface; and a liquid-crystal display element provided with a reflection layer and disposed in tight contact on the lower surface of the light guide plate through a bonding layer, the bonding layer having refractive index in a range of from 1.40 to 1.55 and whole light transmittivity in a range of not less than 90%.
According to the present invention, it is possible to obtain a reflection type liquid-crystal display unit in which the out-going light from the lower surface of the light guide plate is superior in directivity in the vertical direction, wherein the leakage light from the upper surface hardly overlaps a display image. As a result, it is possible to obtain a reflection type liquid-crystal display unit which is superior in lighting availability, superior in contrast viewing at the time of not-lighting, at the time of lighting, and between the two, and superior in brightness for displaying, in which the display image through the light guide plate is hardly disordered and therefore superior in clearness.